Outline Outline

The drive train transmits the

power of the engine to the front
wheels.

It is broadly divided into the

following classifications:
FF (Front engine, Front-wheel
drive vehicle) and FR (Front-
engine, Rear-wheel drive
vehicle).
There are manual transmission
and automatic transmission
types.

FF
FR

Note:
In addition to FF and FR, there
are 4WD (4-Wheel Drive) and
MR (Midship engine Rear-wheel
Engine Transaxle Transmission drive) vehicles.
Drive shaft Propeller shaft Differential
Axle shaft Axle Tires & wheels

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Outline Outline
Power Transmission

FF (Front-engine Front-wheel
drive vehicle) with MT
1.Engine
2.Clutch
3.Manual transaxle
4.Drive shaft
5.Axle
6.Tires & wheels

FF (Front-engine Front-wheel
drive vehicle) with AT

FR (Front-engine Rear-wheel
drive vehicle) with MT

FR (Front-engine Rear-wheel
drive vehicle)with AT

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Clutch Clutch Construction
The clutch of a manual
transmission vehicle enables the
power of the engine to be
engaged or disengaged by the
operation of the clutch pedal

Clutch pedal
Push rod
Master cylinder
Hydraulic hose
Release cylinder
Release fork
Clutch cover

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Clutch Clutch Construction
Parts of the Clutch
Boot
Release fork
Clip
Release bearing
Clutch cover
Clutch disk
Fly wheel
Diaphragm spring
Pressure plate
Clutch Construction Operation Flow
Clutch operation flow
The clutch consists of a portion
that operates mechanically to
transmit power, and a portion
that utilizes hydraulic pressure to
transmit power.

Mechanical operation
Hydraulic operation
Mechanical operation

Clutch pedal
Push rod
Master cylinder
Hydraulic hose
Release cylinder
Release fork
Release bearing
Diaphragm spring
Pressure plate
Clutch disc

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Transaxle Transaxle
A transaxle, in which the
transmission and differential are
integrated, is used on front-
wheel drive vehicles & midship
vehicles.

Transmission
Differential

Input shaft
Output shaft

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Manual Transaxle Manual Transaxle
A manual transaxle engages
and disengages the power and
changes the combinations of the
gears that are meshed. As a
result, it can change the strength
of power, rotational speed, and
the direction of the rotation.

Engine
Clutch
Input shaft
Hub sleeves
Shift lever
Output shaft
Differential
Drive shafts
Tires

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Manual Transaxle Manual Transaxle
Manual transaxle operation

Neutral

1st gear

3rd gear

Reverse

Input shaft
Output shaft
Differential

Blue arrow: transmission of power

Red arrow: direction of rotation
Manual Transaxle Manual Transaxle
SMT (Sequential Manual
Transmission)
The SMT operates the
accelerator, clutch, and shift
operation during a gear change
through a ECU (Electronic
Control Unit).

Features:

There is no clutch pedal.

Gear changes are effected by
operating a switch.

Shift Lever (Switch)

Sensors
ECU (Electronic Control Unit)
Hydraulic pump
Actuator
Engine
Clutch
Transmission

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Automatic Transaxle Automatic Transaxle
An automatic transaxle consists
of a torque converter, planetary
gear unit, and hydraulic control
system.

It uses hydraulic pressure to

automatically shift gears in
accordance with the vehicle
speed, accelerator opening, and
shift lever position. Therefore it
is unnecessary to shift gears as
in the manual transaxle; it is not
even equipped with a clutch.
It also uses a computer to
regulate shifting in accordance
with the driving conditions
detected by sensors. This
system is called ECT
(Electronically Controlled
Transmission).

Torque Converter Oil Pump

Planetary Gear Unit Vehicle speed sensor
Counter gear speed sensor Input turbine speed sensor
Sensors Engine & ECT ECU (Electronic Control Unit)
Solenoid valves Hydraulic Control Unit
Shift Lever
Automatic Transaxle Automatic Transaxle
Full hydraulically-controled
automatic transaxle
The construction of the full
hydraulically-controlled
automatic transaxle is basically
the same as the ECT
(Electronically Controlled
Transmission). However, this
transaxle mechanically controls
shifting by detecting the vehicle
speed hydraulically from the
governor valve, and delects the
accelerator opening from the
amount of movement of the
throttle cable.

Torque Converter
Oil Pump
Planetary Gear Unit
Governor valve
Accelerator pedal
Engine
Throttle cable
Hydraulic Control Unit
Shift Lever
Automatic Transaxle Torque Converter
The torque converter of an
automatic transaxle vehicle
transmits the power of the
engine to the transaxle by
utilizing the force of the fluid. Its
principle can be equated to a
pair of fans that face each other.
One fan blows air to turn the
other fan. The rotation of the
pump impeller applies a
centrifugal force to the fluid,
which transmits the power to the
turbine runner.

Note:
There is also a type of torque
converter that has a lockup
mechanism to mechanically
transmit the power without using
the fluid. This is accomplished
by the operation of the clutches
that switch the paths of power
Pump impeller (from engine) Turbine runner (to transaxle)
transmission, and by directly
Stator Front cover coupling the turbine runner with
Lockup clutch the front cover.

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Automatic Transaxle Oil Pump
The oil pump is driven by the
torque converter to supply the
hydraulic pressure that is
required for the operation of the
automatic transmission.

Front body
Driven gear
Drive gear

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Automatic Transaxle Planetary Gear Unit
This unit shifts the gears in the
automatic transmission. It uses
hydraulic pressure to hold one of
the three types of gears (pinion
gear, sun gear, or ring gear)
stationary in order to create the
following conditions as desired:
deceleration, direct coupling,
and reverse rotation.

Reference:
The shifting operation is explained by
a model comprising a set of
planetary gears.

Deceleration

Direct coupling

Reverse Rotation

Note:
The reference uses a model to
explain the operation using
different input and output shafts.
Click on the underlined hyperlinks as appropriate. In an actual vehicle, the
construction is more complex in
order to enable the planetary
Intermediate shaft Planetary carrier Front sun gear gear unit to appropriately shift
Rear sun gear Ring gear Pinion gear (short) gears, as shown by the left
Pinion gear (long) diagram.

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Automatic Transaxle Planetary Gear Unit
Deceleration

Power input: ring gear

Power output: planetary carrier
Stationary: sun gear

When the sun gear is held

stationary, only the pinion gear
rotates and revolves. Therefore,
the output shaft decelerates in
proportion to the input shaft only
by the rotation of the pinion gear.
Automatic Transaxle Planetary Gear Unit
Direct Coupling

Power input: sun gear, ring gear

Power output: planetary carrier

Ring gear rotates with the locked

planetary carrier, the input and
output shafts rotate at the same
rate.
Automatic Transaxle Planetary Gear Unit
Reverse Rotation

Power input: sun gear

Power output: ring gear
Stationary: Planetary carrier

When the planetary carrier is

fixed in position and the sun
gear turns, the ring gear turn on
its axis and the rotational
direction is reversed.
Automatic Transaxle Hydraulic Control Unit
This component controls the
hydraulic (line) pressure that
operates the planetary gear unit.

Representative valves
Primary regulating valve
Regulates the hydraulic pressure
from the oil pump to create line
pressure.

Shift valve
Shifts gears.

Manual valve
Switches the line pressure paths
in accordance with the
movement of the shift lever.

Solenoid valve
Switches hydraulic paths to shift
gears by receiving the signals
from the ECU (Electronic Control
Unit).

Oil pump
Engine & ECT ECU
(Electronic Control Unit)
Shift lever

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Automatic Transaxle Engine & ECT ECU (Electronic
Control Unit)
This computer receives electric
signals from the sensors,
transmits them to the solenoid
valves in the hydraulic control
unit, and controls the shifting of
the gears.

Sensors
Detect the vehicle speed and
accelerator opening among
other things, and transmit
electrical signals to the ECU.

Representative sensors
Neutral start switch
Detects the shift lever position.
Throttle position sensor
Detects the throttle opening.
Speed sensor
Detects the vehicle speed.
Input shaft speed sensor
Detects the speed of the input
shaft.

Engine
Automatic transaxle
Shift lever
Solenoid valve

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Differential Differential
The differential has the following
three functions:

Deceleration function
Further decelerates the
rotational movement that has
been changed by the
transmission in order to increase
torque.

Differential function
This function adjusts the
rotational differential between
the right and left wheels while
the automobile is cornering.
Without the differential function,
the tires will slip and the vehicle
will not be able to smoothly
complete the turn.

Drive force direction

conversion function (on an FR
vehicle)
This function changes the
rotational force from the
transmission in a right angle and
transmits it to the drive wheels .

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Differential Operation
The differential gears consist of
side gears and a pinion gear.
These gears automatically
regulate the rotational difference
between the right and left wheels
while the automobile is
cornering.

FF (Front-engine front-wheel
drive vehicle)
FR (Front-engine rear-wheel
drive vehicle)

Propeller shaft
Drive gear / Drive pinion
Ring gear
Pinion gear
Side gear
Drive shaft

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Differential LSD (Limited Slip Differential)
A vehicle will not be able to
move when one of its wheels
freewheels in the mud, etc, due
to the function of the differential.
The LSD restrains the function
of the differential in order to
apply the power to both wheels.

Types:
1. Viscous coupling type
2. Torque sensing type
3. Preload type

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Propeller Shaft Propeller Shaft (For FR Vehicle)
The propeller shaft transmits the
power from the transmission to
the differential on an FR (Front-
engine, Rear-wheel drive)
vehicle. Universal joints are
used at the areas where the
shaft joins in order to smoothly
transmit the power even if the
angle of the propeller shaft
changes due to the vertical
movement of the differential.

The propeller shaft comes with

two or three joints.
Flexible couplings may be used
at the joints.

3-joint type
2-joint type

Universal Joints
Center Bearing
Sleeve Yoke
Flexible Coupling

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Propeller Shaft Universal Joint
This joint smoothly transmits the
power by adapting to the joining
angle of the propeller shaft.

Sleeve Yoke
Spider Bearings
Spider

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Drive Shaft Drive Shaft
The drive shafts transmit the
rotation of the engine to the
wheels via the transmission and
differential. They are used on
vehicles with drive wheels that
are supported by an
independent suspension system.

Note:
An axle shaft is used on a
vehicle with a rigid type
suspension.

Differential
Drive Shafts
Axle Shafts
Axle Housing

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Drive Shaft Drive Shaft
Type of drive shaft joints
Rzeppa (Birfield) Joint
Uses several steel balls and
excels in constant velocity
performance.

Tripod Joint
Uses three sliding rollers and is
slightly inferior to the Rzeppa
joint in constant velocity
performance. It has a simple
construction and can be slid
axially.

Cross Groove Joint

Uses several steel balls and
excels in vibration, noise, and
constant velocity performance.

Sliding rollers
Steel balls
Axle Axle
The axle and axle shaft support
the wheel and the drive shafts.

A. Tapered roller bearing type

Axle
Tapered roller bearing

B. Angular ball bearing type

C. Housing type rigid
suspension type

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